I agree or maybe a 96 hour level design contest or something like that being similar to a 24 hour level design contest with a theme that is a little bit more complex. How about something like that but with a strawberry ice cream cone level? Wasn't there something like that once?
As with previous years, it was only announced as it started since it's a just a surprise-mini-fun-event-thing. It didn't quite make it as far as being posted about on Twitter when it started, but you would've got an @everyone ping in #announcements.
The big contests and things all of course get announced prior, but silly little events like this are sometimes best held as a surprise so they're more fun.